The present invention relates to equipment and methods to fabricate orthognathic surgical splints, and to a related technique for creating a computerized composite skull model useful for diagnosis and treatment planning.
Surgical planning for orthognathic surgery traditionally combines various diagnostic methods to achieve the final surgical plan. Anthropometric measurements are manually taken on the patient at clinical examinations. Cephalometric radiographs are analyzed with angular and linear measurements. Facial aesthetics are evaluated by direct visual inspection and photography. Plaster dental models are conventionally used to analyze patient""s dentition. Video imaging techniques may be used to estimate the movements resulting from the surgery and to predict soft tissue changes. Used together, these diagnostic methods allow the clinicians to plan surgical movements of the patient""s jaws and teeth in all dimensions.
As indicated above, plaster dental models are conventionally used to replicate the patient""s teeth. Since plaster dental models lack bony support, these models are of limited value because the clinicians cannot visualize the surrounding bony structures, which are critical to the treatment of complex cranio-maxillofacial deformities. A conventional plaster dental model mounted on articulators is shown in FIG. 1.
Surgical splints fabricated from plaster dental models nevertheless are used to transfer the treatment plan to the patient in the operating room. The thin acrylic splint contains indentations of the incisal edges and cusps of the teeth, and ideally provides for precise positioning of the upper jaw relative to the lower jaw. Most commonly, intermediate splints are used to position an osteotomized maxilla to an uncut mandible, and final splits are used to align the mandible to the repositioned maxilla. The problem remains that the splints fabricated from the plaster dental models do not properly position the jaws relative to the remaining structure of the skull.
Clinicians have attempted to create physical skull models which depict both the patient""s bone structure and dentition. Several investigators have attempted to incorporate plaster dental models into physical milled stereolithographic skull models, as indicated in an article published in J Oral Maxillofac Surg, Volume 77, page 662. A physical skull model with a plaster dental model mounted on articulators may cost $2,000.00 or more. Various other publications discuss the creation of physical composite skull models. Since all these methods are based on creating physical models, the high cost and limited flexibility of the models have highly restricted their use.
The disadvantages of the prior art are overcome by the present invention, and improved methods and apparatus are hereinafter disclosed for fabricating stereolithographic orthognathic surgical splints from digital dental models, and for combining digital dental models with three-dimensional computed tomography (CT) models.
According to a preferred embodiment of the invention, a computerized treatment plan for each patient involves the creation of one or more stereolithographic surgical splints. These splints are computer generated and digitally fabricated, and are therefore highly accurate. According to the present invention, diagnosis, surgical planning and simulation, and the fabrication of surgical splints may be accomplished using a computer and an SLA machine. Accordingly, patients with craniofacial and maxillofacial facial deformities may be scanned to obtain three-dimensional CT data, and their dentition may be laser scanned. Computerized virtual osteotomies may be performed on a computerized CT skull model, and the treatment plan may be transferred to the patient through the intermediate and final surgical splints, which are computer generated and then digitally fabricated. The techniques of the present invention for generating surgical splints may replace traditional plaster dental model surgery, as discussed above.
The computerized composite skull model of the present invention combines three-dimensional CT bone model data with digital dental model data. The composite skull model may be used for accurate visualization during diagnosis and treatment planning. The computerized composite skull model may be used to generate a stereolithographic model of the patient""s craniofacial skeleton and dentition, and may be used to improve surgical outcomes with reduced operating time.
It is an object of the present invention to provide an improved process for forming a surgical splint which will receive a patient""s dentition and thereby properly align both the upper and lower jaw relative to the patient""s skull. A three dimensional computed tomography model of bone structure for the patient""s upper jaw, lower jaw, and at least a portion of the skull may be generated. A digital dental computer model may also be generated of the patient""s dentition utilizing laser surface scanning. The computed tomography computer model and the digital dental computer model may then be combined to form a composite computer model. The two models may be aligned utilizing fiduciary markers. The composite model may then be displayed, and the clinician may reposition at least one of the upper and the lower jaw relative to the patient""s skull to form a planned position computer model. Using this planned position computer model, a computer model surgical splint may be formed. The computer model surgical splint may then used to generate a physical surgical splint.
It is a feature of the present invention that the composite computer model may be used by the clinician in various ways to assist in diagnosis, surgical planning, and simulation of surgical outcomes.
A significant feature of the present invention is that highly reliable positioning of the upper jaw and lower jaw relative to the skull is obtained using a surgical splint which is manufactured using a combination of the CT model data and the digital dental model data.
A significant advantage of the present invention is that the substantial costs and limited flexibility of plaster dental models and stereolithographic skulls models may be voided.
These and further objects, features, and advantages of the invention will become apparent from the following detailed description wherein reference is made to the figures in the accompanying drawings.